The present invention relates to a production method of a 5-phthalancarbonitrile compound useful as an intermediate for citalopram, which is an antidepressant, an intermediate for the 5-phthalancarbonitrile compound and a production method of the intermediate for the 5-phthalancarbonitrile compound. More particularly, the present invention relates to a production method of a 5-phthalancarbonitrile compound via a novel compound of the formula [I] to be mentioned later, based on a completely new viewpoint.
The 5-phthalancarbonitrile compound of the formula [VI]
(hereinafter to be also referred to as compound [VI]) is a compound useful as a synthetic intermediate for citalopram of the formula [VII]
which is an antidepressant. The production method of the 5-phthalancarbonitrile compound is known to be as shown in the following scheme (WO98/19511). 
wherein R is cyano, alkyloxycarbonyl having 2 to 6 carbon atoms or alkylaminocarbonyl having 2 to 6 carbon atoms, and Hal is a halogen atom.
According to this method, when R is other than cyano, cyanation is necessary after reduction and ring closure reaction. For example, when R is alkyloxycarbonyl, cyanation is carried out by the three steps of hydrolysis, amidation and reaction with chlorosulfonyl isocyanate, and when R is alkylaminocarbonyl, cyanation is carried out by a reaction with thionyl chloride or phosphorus pentachloride. In these methods, reagents undesirable to the environment, such as chlorosulfonyl isocyanate, thionyl chloride and phosphorus pentachloride, are used, and when R is alkyloxycarbonyl, cyanation is carried out by 3 steps, which is not necessarily simple or easy.
When R is cyano, the production method of the starting material, 5-cyanophthalide, needs to be improved. To be specific, 5-cyanophthalide is known to be obtained by the reaction of a diazonium salt derived from 5-aminophthalide with potassium cyanide in the presence of copper sulfide (Bull. Soc. Sci. Bretagne, 26, 1951, 35). This method is not desirable in that a toxin and a heavy metal salt are involved, such as potassium cyanide and copper sulfide. In addition, synthesis of 5-aminophthalide requires a dangerous reaction of nitration of phthalimide (Organic Synthesis II, 459), and further, reduction to amino by tin chloride and semi-reduction of phthalimide by zinc (J. Chem. Soc., 1931, 867), generating a waste heavy metal that is industrially undesirable.
It is therefore an object of the present invention to provide a production method of a 5-phthalancarbonitrile compound, which places only a small burden on the environmental and which is safe.
Such object can be achieved by the present invention detailed in the following.
In accordance with the present invention, there are provided a method of producing a 5-phthalancarbonitrile compound (compound of the aforementioned formula [VI]) useful as an intermediate for citalopram, which is safe and imposes less environmental burden, the method comprising using a compound of the formula [A]
wherein R2 is alkanoyl having 2 to 5 carbon atoms (hereinafter to be also referred to as compound [A]) as a starting material, and a novel compound of the formula [I]
wherein X is chlorine atom, bromine atom or iodine atom (hereinafter to be also referred to as compound [I]) as a key intermediate, without using thionyl chloride and the like; novel compounds of the following formulas [II], [III], [IV] and [V], that can be used for the production method of the 5-phthalancarbonitrile compound of the present invention: 
wherein R1 is alkanoyl having 2 to 5 carbon atoms, alkyl having 1 to 5 carbon atoms, tetrahydropyran-2-yl, alkoxymethyl wherein the alkoxyl moiety has 1 to 5 carbon atoms, 1-alkoxyethyl wherein the alkoxyl moiety has 1 or 3 to 10 carbon atoms, or trialkylsilyl wherein each alkyl moiety has 1 to 5 carbon atoms, and X is chlorine atom, bromine atom or iodine atom (hereinafter to be also referred to as compound [II], compound [III], compound [IV] and compound [V], respectively); and the production methods thereof. Every conventional production method of citalopram goes through a 5-substituted phthalide compound (e.g., 5-formylphthalide), but the method of the present invention goes through the compound [I], employing a completely new synthetic strategy.
The symbols used in the present specification are defined in the following.
With regard to alkyl, alkoxy and the like used in the present invention, they are linear unless a prefix (e.g., iso, neo etc.) or a symbol (e.g., sec-, tert- etc.) is attached. For example, a simple xe2x80x9cpropylxe2x80x9d means linear propyl.
The alkanoyl having 2 to 5 carbon atoms at R1, R2, R1xe2x80x2 and R1a is linear or branched chain alkanoyl preferably having 2 to 5 carbon atoms, such as acetyl, butanoyl, propanoyl, isopropanoyl, pentanoyl, pivaloyl and the like, with preference given to acetyl, propanoyl and pivaloyl.
The alkyl having 1 to 5 carbon atoms at R1, R1xe2x80x2 and R1b is linear or branched chain alkyl preferably having 1 to 4 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl and the like, with preference given to methyl and tert-butyl.
The alkoxymethyl at R1, R1xe2x80x2 and R1b, wherein the alkoxyl moiety has 1 to 5 carbon atoms, is alkoxymethyl having linear or branched chain alkoxy preferably having 1 or 2 carbon atoms, such as methoxymethyl, ethoxymethyl, propoxymethyl, isopropoxymethyl, butoxymethyl, isobutoxymethyl, sec-butoxymethyl, tert-butoxymethyl, pentoxymethyl, isopentoxymethyl and the like, with preference given to methoxymethyl and ethoxymethyl.
The 1-alkoxyethyl at R1, wherein the alkoxyl moiety has 1 or 3 to 10 carbon atoms, is linear, branched chain or cyclic 1-alkoxyethyl wherein the alkoxyl moiety preferably has 1 or 3 to 6 carbon atoms, such as 1-methoxyethyl, 1-propoxyethyl, 1-isopropoxyethyl, 1-butoxyethyl, 1-isobutoxyethyl, 1-sec-butoxyethyl, 1-tert-butoxyethyl, 1-pentoxyethyl, 1-isopentoxyethyl, 1-hexyloxyethyl, 1-cyclohexyloxyethyl, 1-heptyloxyethyl, 1-octyloxyethyl, 1-nonyloxyethyl, 1-decyloxyethyl and the like, with preference given to 1-propoxyethyl, 1-butoxyethyl and 1-cyclohexyloxyethyl.
The 1-alkoxyethyl at R1xe2x80x2 and R1b, wherein the alkoxyl moiety has 1 to 10 carbon atoms, is linear, branched chain or cyclic 1-alkoxyethyl wherein the alkoxyl moiety preferably has 1 to 6 carbon atoms, such as 1-methoxyethyl, 1-ethoxyethyl, 1-propoxyethyl, 1-isopropoxyethyl, 1-butoxyethyl, 1-isobutoxyethyl, 1-sec-butoxyethyl, 1-tert-butoxyethyl, 1-pentoxyethyl, 1-isopentoxyethyl, 1-hexyloxyethyl, 1-cyclohexyloxyethyl, 1-heptyloxyethyl, 1-octyloxyethyl, 1-nonyloxyethyl, 1-decyloxyethyl and the like, with preference given to 1-ethoxyethyl, 1-propoxyethyl, 1-butoxyethyl and 1-cyclohexyloxyethyl.
The alkyl of the trialkylsilyl at R1, R1xe2x80x2 and R1b, wherein each alkyl moiety has 1 to 5 carbon atoms, is independently linear or branched chain alkyl preferably having 1 to 4 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl and the like, with preference given to methyl and tert-butyl. The trialkylsilyl may be, for example, trimethylsilyl, triethylsilyl, tripropylsilyl, triisopropylsilyl, tributylsilyl, triisobutylsilyl, trisec-butylsilyl, tripentylsilyl, triisopentylsilyl, tert-butyldimethylsilyl and the like, with preference given to trimethylsilyl, tributylsilyl and tert-butyldimethylsilyl.
The present invention is explained in detail in the following.
Production Method of Compound [I]
The novel compound [I] can be efficiently obtained by subjecting compound [A] to one of chlorination, bromination and iodination, and then to the elimination of the alkanoyl group. For example, chlorination, bromination or iodination, preferably bromination, is performed by reacting compound [A] with a halogenating agent in a reaction solvent to give a compound of the formula [II-a]
wherein X is chlorine atom, bromine atom or iodine atom and R1a is alkanoyl having 2 to 5 carbon atoms (hereinafter to be also referred to as compound [II-a]). This reaction is preferably carried out in the presence of a base. As used herein, X is preferably bromine atom in consideration of conversion of the compound of the formula [II-b] to a lithium compound or a Grignard reagent in the later step and R1a is particularly preferably acetyl in view of the easiness of synthesis and deprotection. The alkanoyl group is eliminated by adding the obtained compound [II-a] or a solution of compound [II-a] in an organic solvent, to an aqueous solution of an acid or base, preferably an acidic aqueous solution, to allow hydrolysis.
The starting compound [A] is preferably m-xylylene glycol diacetate, m-xylylene glycol dipropionate or m-xylylene glycol dipivalate.
The reaction solvent to be used for chlorination, bromination and iodination is, for example, glacial acetic acid, aqueous acetic acid solution (concentration: 60-100 wt %, preferably 80-100 wt %), water, monochlorobenzene, o-dichlorobenzene, ethyl acetate, tert-butyl methyl ether, and methanol, ethanol, isopropyl alcohol, acetone etc., that may contain water, with preference given to glacial acetic acid, aqueous acetic acid solution, methanol, o-dichlorobenzene and ethyl acetate. The reaction solvent is used in an amount of generally 1 L-20 L, preferably 3 L-10 L, per 1 kg of compound [A].
The base to be used for chlorination, bromination and iodination is sodium acetate, potassium acetate, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium methoxide, sodium ethoxide and the like, preferably sodium acetate, potassium acetate, sodium hydroxide, potassium hydroxide, sodium carbonate and potassium carbonate. The base is used in an amount of generally 0.1 equivalent-10 equivalents, preferably 0.8 equivalent-6 equivalents, per the amount of compound [A].
The halogenating agent to be used for chlorination, bromination and iodination is bromine, chlorine, N-bromosuccinimide, N-chlorosuccinimide, sulfuryl chloride and the like, preferably bromine and N-bromosuccinimide. The halogenating agent is used in an amount of generally 0.8 mol-8 mol, preferably 2 mol-6 mol, per 1 mol of compound [A].
For chlorination and bromination, a catalyst may be added to accelerate the reaction. The catalyst may be a single metal such as iron, copper, zinc, aluminum and the like; or a metal halide such as iron(I) chloride, iron(II) chloride, aluminum chloride, aluminum bromide, copper(I) chloride, copper(II) chloride, magnesium chloride, magnesium bromide, magnesium iodide, titanium tetrachloride, zinc chloride, zinc bromide, zinc iodide and the like, with preference given to iron, iron(I) chloride, iron(II) chloride, magnesium chloride, magnesium bromide, zinc chloride, zinc bromide and zinc iodide. The catalyst is used in an amount of generally 0.0001 mol-0.5 mol, preferably 0.001 mol-0.2 mol, per 1 mol of compound [A].
The reaction temperature of chlorination, bromination and iodination is generally from xe2x88x9230xc2x0 C. to 80xc2x0 C., preferably from 0xc2x0 C. to 50xc2x0 C., and the reaction time is generally 30 min-24 hr, preferably 2 hr-18 hr.
When compound [A] is subjected to chlorination, bromination or iodination, a 2,6-disubstituted compound may be produced as a halide, besides the compound [II-a] which is a 2,4-disubstituted compound. Such halide is isolated by, for example, pouring the reaction mixture to a reducing aqueous solution (e.g., aqueous sodium sulfite solution and aqueous sodium thiosulfate solution etc.) under ice-cooling, or pouring a reducing aqueous solution into the reaction mixture, adding an organic solvent, extraction and evaporation of the solvent. The compound [II-a] can be isolated from the mixture of halide by silica gel column chromatography, recrystallization and the like. The compound [II-a] may or may not be isolated from the mixture of halide. When the compounds are subjected to the next step without isolation, the corresponding 2,6-disubstituted compound, such as 2,6-disubstituted compound of compound [I] and 2,6-disubstituted compound of the compound of the formula [II-b] to be mentioned later, is obtained in each step together with the reaction product.
The amount of water to be used for elimination of the alkanoyl group is generally 0.5 L-20 L, preferably 3 L-10 L, per 1 kg of halide (mixture when halide is a mixture). A solvent inert to the reaction may be concurrently used, such as alcohol solvent (e.g., methanol, ethanol etc.), tetrahydrofuran (THF), dioxane and the like, which may be used to dissolve halide. When the solvent is used for dissolution of halide, it is used in an amount of generally 0.5 L-20 L, preferably 2 L-10 L, per 1 kg of halide (mixture when halide is a mixture).
The acid to be used for the elimination of the alkanoyl group is not particularly limited as long as it is typically used for this purpose. Examples thereof include inorganic acid such as hydrochloric acid, hydrobromic acid, hydrofluoric acid, sulfuric acid, phosphoric acid and the like; organic acid such as formic acid, acetic acid, propionic acid, trifluoroacetic acid, methanesulfonic acid, trifluoromethanesulfonic acid and the like; and the like, with preference given to hydrochloric acid, hydrobromic acid and sulfuric acid. The amount of the acid to be used is generally 0.001 kg-10 kg, preferably 0.01 kg-0.3 kg, per 1 kg of halide (mixture when halide is a mixture).
The base to be used for the elimination of the alkanoyl group is not particularly limited as long as it is typically used for this purpose. Examples thereof include inorganic base such as hydroxide, carbonate or hydrogencarbonate of alkali metal (e.g., lithium, sodium, potassium etc.) or alkaline earth metal (e.g., calcium, magnesium etc.) and alkoxide (e.g., methoxide, ethoxide etc.) of alkali metal, and organic base such as trialkylamine (e.g., trimethylamine, triethylamine etc.), with preference given to sodium hydroxide, potassium hydroxide, potassium carbonate and sodium methoxide. The amount of the base to be used is generally 0.8 equivalent-10 equivalents, preferably 1 equivalent-5 equivalents, per halide (mixture when halide is a mixture).
The reaction temperature of the elimination of the alkanoyl group is generally from xe2x88x9220xc2x0 C. to 100xc2x0 C., preferably from 10xc2x0 C. to 80xc2x0 C., and the reaction time is generally 10 min-24 hr, preferably 30 min-8 hr.
The compound [I] is isolated by a conventional method, such as crystallization after neutralization of the reaction mixture.
Production Method of Compound [IIxe2x80x2]
A compound of the formula [IIxe2x80x2]
wherein R1xe2x80x2 is alkanoyl having 2 to 5 carbon atoms, alkyl having 1 to 5 carbon atoms, tetrahydropyran-2-yl, alkoxymethyl wherein the alkoxyl moiety has 1 to 5 carbon atoms, 1-alkoxyethyl wherein the alkoxyl moiety has 1 to 10 carbon atoms, or trialkylsilyl wherein each alkyl moiety has 1 to 5 carbon atoms, and X is chlorine atom, bromine atom or iodine atom (hereinafter to be referred to as compound [IIxe2x80x2]), consists of compound [II-a] and a compound of the formula [II-b]
wherein R1b is alkyl having 1 to 5 carbon atoms, tetrahydropyran-2-yl, alkoxymethyl wherein the alkoxyl moiety has 1 to 5 carbon atoms, 1-alkoxyethyl wherein the alkoxyl moiety has 1 to 10 carbon atoms or trialkylsilyl wherein each alkyl moiety has 1 to 5 carbon atoms, and X is chlorine atom, bromine atom or iodine atom (hereinafter to be referred to as compound [II-b]). A compound wherein only 1-ethoxyethyl is excluded from the substituents at R1xe2x80x2 of compound [IIxe2x80x2] corresponds to novel compound [II]. The compound [IIxe2x80x2] can be obtained by
(a) converting the hydroxyl group of compound [I] to alkoxy having 1 to 5 carbon atoms, tetrahydropyran-2-yloxy, alkoxymethoxy wherein the alkoxyl moiety has 1 to 5 carbon atoms, 1-alkoxyethoxy wherein the alkoxyl moiety has 1 to 10 carbon atoms or trialkylsilyloxy wherein each alkyl moiety has 1 to 5 carbon atoms, or by
(b) subjecting compound [A] to chlorination, bromination or iodination.
The step (a) is explained in the following. By (a), compound [II-b] can be obtained. The hydroxyl group can be converted to each group by any method generally used for converting hydroxyl group to such group. It is converted to 1-alkoxyethoxy by, for example, reacting compound [I] with alkyl vinyl ether of the formula :R3CHxe2x95x90CH2 wherein R3 is alkoxy having 1 to 10 carbon atoms, in a reaction solvent in the presence of a catalyst.
The starting compound [I] is preferably 2,4-bis(hydroxymethyl)bromobenzene in consideration of conversion to a lithium compound or a Grignard reagent of the compound [III] in the later step.
The alkoxy having 1 to 10 carbon atoms at R3 of the above formula corresponds to alkoxy of 1-alkoxyethyl at the substituent R1xe2x80x2 in compound [IIxe2x80x2], wherein the alkoxyl moiety has 1 to 10 carbon atoms. The alkyl vinyl ether to be used for the reaction is, for example, methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, isopropyl vinyl ether, butyl vinyl ether, pentyl vinyl ether, cyclohexyl vinyl ether, hexyl vinyl ether, heptyl vinyl ether, octyl vinyl ether, nonyl vinyl ether, decyl vinyl ether and the like, preferably ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether or cyclohexyl vinyl ether. The amount of the alkyl vinyl ether to be used is generally 2 mol-4 mol, preferably 2 mol-3 mol, per 1 mol of compound [I].
As the catalyst, for example, p-toluenesulfonic acid, methanesulfonic acid, sulfuric acid, hydrochloric acid, trifluoroacetic acid, trifluoromethanesulfonic acid, and an acidic ion exchange resin such as Amberlyst 15E, Amberlite IR-118 etc. are used, with preference given to p-toluenesulfonic acid, methanesulfonic acid, sulfuric acid and hydrochloric acid. These catalysts can be also used in the form of a hydrate. The amount of the catalyst to be used is generally 0.0001 mol-0.2 mol, preferably 0.0005 mol-0.01 mol, per 1 mol of compound [I].
The reaction solvent may be, for example, toluene, xylene, monochlorobenzene, methylene chloride, acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate and the like, with preference given to toluene, xylene, monochlorobenzene and methylene chloride. The amount of the reaction solvent to be used is generally 1 L-20 L, preferably 2 L-12 L, per 1 kg of compound [I].
The reaction temperature is generally from xe2x88x9220xc2x0 C. to 120xc2x0 C., preferably from 0xc2x0 C. to 60xc2x0 C., and the reaction time is generally 10 min-10 hr, preferably 30 min-6 hr. The objective compound can be isolated by a conventional method (e.g., extraction, etc.).
Conversion to a group other than 1-alkoxyethoxy is performed according to a conventional method. For the conversion to alkoxy, for example, a reagent such as R4OH wherein R4 is alkyl having 1 to 5 carbon atoms, R4Br wherein R4 is as defined above, R4I wherein R4 is as defined above, and (R4)2SO4 wherein R4 is as defined above is used; for the conversion to tetrahydropyran-2-yloxy, for example, a reagent such as 3,4-dihydro-2[H]-pyran is used; for the conversion to alkoxymethoxy, for example, a reagent, such as R5OCH2OH wherein R5 is alkyl having 1 to 5 carbon atoms, R5OCH2OR5 wherein R5 is as defined above, R5OCH2Cl wherein R5 is as defined above and R5OCH2Br wherein R5 is as defined above is used; and for the conversion to trialkylsilyloxy, for example, a reagent, such as (R6)3SiCl wherein R6 is alkyl having 1 to 5 carbon atoms, is used. The definition of the above R4-R6 is the same as in the corresponding R1xe2x80x2.
Then, compound [II-a] can be obtained by (b). The chlorination, bromination and iodination of compound [A] in (b) are carried out in the same manner as in those for the production of compound [I]. Bromination is preferably carried out in consideration of conversion of the compound [II-b] to a lithium compound or a Grignard reagent in the later step.
The compound [II-b] can be also obtained by a method other than the above-mentioned (a). For example, a compound [II-b] wherein R1b is alkyl having 1 to 5 carbon atoms can be obtained by Step 1: m-xylylene dichloride is reacted with an alkali metal alkoxide of the formula Rxe2x80x2OM, wherein Rxe2x80x2 is alkyl having 1 to 5 carbon atoms and M is alkali metal, in a reaction solvent to give 1,3-bis(alkoxymethyl)benzene, and Step 2: the resulting compound is subjected to chlorination, bromination or iodination.
Step 1 is explained in detail in the following. In this step, alkali metal alkoxide is added to m-xylylene dichloride in a reaction solvent to give 1,3-bis(alkoxymethyl)benzene.
The reaction solvent in Step 1is exemplified by alcohol solvent (e.g., methanol, ethanol, isopropyl alcohol, tert-butyl alcohol etc.), tetrahydrofuran (THF), tert-butyl methyl ether, toluene, monochlorobenzene, N,N-dimethylformamide, dimethyl sulfoxide and the like. The amount of the solvent to be used is generally 1 L-30 L, preferably 2 L-15 L, per 1 kg of m-xylylene dichloride.
The alkyl moiety of the alkali metal alkoxide in Step 1 is the same as those exemplified for the alkyl at R1b and examples of alkali metal include sodium, potassium and the like. Preferable examples of alkali metal alkoxide include sodium methoxide and potassium tert-butoxide. The amount of the alkali metal alkoxide to be used is generally 1.8 mol-4 mol, preferably 2 mol-3.2 mol, per 1 mol of m-xylylene dichloride.
The reaction temperature in Step 1 is generally from xe2x88x9230xc2x0 C. to 100xc2x0 C., preferably 20xc2x0 C.-70xc2x0 C., and the reaction time is generally 0.5 hr-10 hr, preferably 1 hr-6 hr.
The isolation of 1,3-bis(alkoxymethyl)benzene can be carried out by a conventional method, such as extraction and drying after evaporation of the solvent.
Step 2 can be carried out in the same manner as in chlorination, bromination, iodination in the production method of compound [I] and under the same reaction conditions. The reaction solvent, base, halogenating agent and catalyst to be used for the chlorination, bromination and iodination are the same as those exemplified for the production method of compound [I], wherein they are used in the same amounts as in the production method of compound [I]. The reaction product can be isolated in the same manner as in the production method of compound [I].
Production Method of Compound [III]
A novel compound [III] can be obtained by
(a) converting compound [II-b] to Grignard reagent or lithium compound,
(b) coupling the resulting compound with p-fluorobenzaldehyde and
(c) subjecting the obtained coupling compound to deprotection of R1b and cyclization.
The compound [II-b] is compound [I], wherein hydroxyl group has been protected, which is, after conversion to a lithium compound or a Grignard reagent, reacted with p-fluorobenzaldehyde. Therefore, X in the compound [II-b] is free of any particular limitation as long as compound [II-b] can be converted to a lithium compound or a Grignard reagent. Preferred is bromine atom in view of the quick conversion and the stability of the lithium compound or Grignard reagent after conversion. For easy deprotection, tetrahydropyran-2-yl, alkoxymethyl, where alkoxy has 1 to 5 carbon atoms, 1-alkoxyethyl, where alkoxy has 1 to 10 carbon atoms, and trialkylsilyl, where each alkyl has 1 to 5 carbon atoms, are preferable as R1b, with more preference given to tetrahydropyran-2-yl, methoxymethyl and 1-alkoxyethyl, where alkoxy has 1 to 10 carbon atoms, particularly preferably 1-ethoxyethyl, 1-propoxyethyl, 1-butoxyethyl and 1-cyclohexyloxyethyl. From the easiness of synthesis, methyl and tert-butyl are particularly preferable.
As compound [II-b], preferred are 2,4-bis(1xe2x80x2-ethoxy ethoxymethyl)bromobenzene, 2,4-bis(1xe2x80x2-butoxyethoxymethyl)-bromobenzene and 2,4-bis(1xe2x80x2-cyclohexyloxyethoxymethyl)bromobenzene.
The above-mentioned (a) to (c) are explained in this order in the following. (a): The compound [II-b] can be converted to a Grignard reagent or a lithium compound by a method conventionally known, which is used for obtaining a Grignard reagent or a lithium compound from halide. For example, compound [II-b] is reacted with metal magnesium in an organic solvent, or a solution of an organic lithium compound in an organic solvent, and may be added dropwise to compound [II-b]. The metal magnesium or organic lithium compound is added in an amount generally necessary for converting a halide to a Grignard reagent or a lithium compound. For example, metal magnesium is added in an amount of generally 0.9 mol-3 mol, preferably 1 mol-1.5 mol, and the organic lithium compound is added in an amount of generally 0.9 mol-1.5 mol, preferably 1 mol-1.3 mol, both per 1 mol of compound [II-b]. Examples of the organic lithium compound include n-butyl lithium, phenyl lithium, methyl lithium, sec-butyl lithium and tert-butyl lithium, preferably n-butyl lithium and methyl lithium. For the easiness of the operation and the yield of the reaction, compound [II-b] is preferably converted to a lithium compound.
The organic solvent is exemplified by ether solvents (e.g., tetrahydrofuran (THF), tert-butyl methyl ether, dimethoxyethane, dibutyl ether, ethyl ether etc.), hexane, heptane, toluene, xylene and the like, with preference given to hexane, THF, tert-butyl methyl ether and dimethoxyethane. The amount of the organic solvent to be used is generally 1 L-30 L, preferably 5 L-20 L, per 1 kg of compound [II-b].
The reaction temperature in (a) is generally from xe2x88x9278xc2x0 C. to 30xc2x0 C., preferably from xe2x88x9250xc2x0 C. to xe2x88x9210xc2x0 C., and the reaction time is generally 10 min-6 hr, preferably 10 min-2 hr. The reaction mixture obtained in (a) can be isolated or purified by a conventional method. Alternatively, it may be subjected to the next reaction as it is obtained. (b): p-Fluorobenzaldehyde is added dropwise to the reaction mixture of (a) for coupling reaction. The amount of p-fluorobenzaldehyde to be used is generally 0.8 mol-3 mol, preferably 1 mol-1.5 mol, per 1 mol of compound [II-b]. p-Fluorobenzaldehyde can be added as a solution in an organic solvent, wherein the organic solvent is free of any particular limitation and exemplified by tetrahydrofuran, tert-butyl methyl ether, dimethoxyethane, hexane, heptane and the like.
The reaction temperature in (b) is generally from xe2x88x9278xc2x0 C. to 60xc2x0 C., preferably from xe2x88x9250xc2x0 C. to 30xc2x0 C., and the reaction time is generally 10 min-6 hr, preferably 10 min-2 hr.
After the completion of the reaction, a basic aqueous solution (e.g., aqueous ammonium chloride solution), an acidic aqueous solution (e.g., aqueous acetic acid solution) and the like are added to hydrolyze the reaction product. The coupling compound after hydrolysis can be isolated by, for example, partitioning and evaporation of the solvent. (c): The isolated coupling compound is reacted with an acid catalyst in a reaction solvent for the deprotection of R1b and cyclization. The method of addition is not particularly limited. For example, an acid catalyst may be added to the reaction mixture of the coupling compound. The reaction is preferably carried out under pressure of generally 2 kPa-110 kPa, preferably 5 kPa-80 kPa, while removing deprotected aldehydes having a low boiling point, thereby suppressing the occurrence of by-product.
The reaction solvent may be water alone, because the reaction proceeds sufficiently. A suitable organic solvent may be further added. The organic solvent to be added may be miscible with water or non-miscible with water. Examples thereof include methanol, ethanol, isopropyl alcohol, acetone, tetrahydrofuran, toluene and xylene. The amount of the reaction solvent to be used is generally 0.5 L-20 L, preferably 1 L-10 L, per 1 kg of compound [II-b].
The acid catalyst may be a typical mineral acid, acidic ion exchange resin and Lewis acid, preferably phosphoric acid, sulfuric acid, hydrochloric acid, p-toluenesulfonic acid, methanesulfonic acid, trifluoroacetic acid and trifluoromethanesulfonic acid. The amount of the acid catalyst to be used is generally 0.1 mmol-30 mol, preferably 0.1 mol-20 mol, per 1 mol of compound [II-b]. The acidic catalyst can be also used in the form of an aqueous solution.
The reaction temperature in (c) is generally 30xc2x0 C.-150xc2x0 C., preferably 50xc2x0 C.-100xc2x0 C., and the reaction time is generally 10 min-20 hr, preferably 1 hr-6 hr.
The objective compound (compound [III]) can be isolated by a conventional method (e.g., filtration, recrystallization etc.).
The compound [III] can be obtained via a Grignard reagent or lithium compound of compound [II-b] and then through a coupling compound of the formula 
wherein R1 is as defined above.
Production Method of Compound [IV]
The novel compound [IV] can be obtained by oxidation of compound [III]. The compound [III] has, as an easily oxidizable moiety, the 1-position and 3-position carbons, besides hydroxymethyl at the 5-position of the 1,3-dihydroisobenzofuran ring. Therefore, oxidation of compound [III] may accompany oxidation of the 1-position and 3-position carbons as a side reaction. However, when compound [III] is oxidized with hypochlorite in the presence of an N-oxy radical catalyst, hydroxymethyl is selectively oxidized to give compound [IV] at a high yield. To be specific, hypochlorite is added, preferably added dropwise as an aqueous solution, to a solution of compound [III] in an organic solvent in the presence of a base, a catalyst and an N-oxy radical catalyst, to give compound [IV].
The hypochlorite to be used for the oxidation may be, for example, sodium hypochlorite, potassium hypochlorite, calcium hypochlorite and the like, preferably sodium hypochlorite. The amount of the hypochlorite to be used is generally 0.8 mol-2 mol, preferably 0.85 mol-1.3 mol, per 1 mol of compound [III]. Sodium hypochlorite is preferably used in the form of an aqueous solution, where the concentration of the aqueous solution is generally 8 wt %-15 wt %, preferably 11 wt %-14 wt %.
The N-oxy radical catalyst to be used for the oxidation may be, for example, 4-substituted-2,2,6,6-tetramethyl-1-piperidinoxy. The amount of the catalyst to be used is generally 0.0001 mol-0.1 mol, preferably 0.0001 mol-0.01 mol, per 1 mol of compound [III]. Examples of the 4-position substituent include hydrogen atom, hydroxyl group, alkoxy having 1 to 10 carbon atoms, acyloxy having an aliphatic hydrocarbon residue having 1 to 10 carbon atoms, carbonylamino having an aliphatic hydrocarbon residue having 1 to 10 carbon atoms and the like, particularly preferably hydroxyl group from the viewpoint of the yield.
The alkoxy having 1 to 10 carbon atoms is preferably linear or branched chain alkoxy having 1 to 5 carbon atoms, such as methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, tert-butoxy, pentoxy, isopentoxy, hexyloxy, heptyloxy, octyloxy, nonyloxy and decyloxy, preferably methoxy, ethoxy and isopropoxy.
The acyloxy having an aliphatic hydrocarbon residue having 1 to 10 carbon atoms is linear or branched chain acyloxy having an aliphatic hydrocarbon residue preferably having 1 to 6 carbon atoms, such as acetyloxy, propionyloxy, butyryloxy, isobutyryloxy, valeryloxy, isovaleryloxy, pivaloyloxy, hexanoyloxy, heptanoyloxy, octanoyloxy, nonanoyloxy, decanoyloxy, undecanoyloxy, acryloyloxy and methacryloyloxy, preferably acetyloxy and methacryloyloxy.
The carbonylamino having an aliphatic hydrocarbon residue having 1 to 10 carbon atoms is a linear or branched chain carbonylamino that has aliphatic hydrocarbon residue preferably having 1 to 6 carbon atoms, such as acetylamino, propionylamino, butyrylamino, isobutyrylamino, valerylamino, isovalerylamino, pivaloylamino, hexanoylamino, heptanoylamino, octanoylamino, nonanoylamino, decanoylamino, undecanoylamino, acryloylamino and methacryloylamino, preferably acetylamino.
Examples of 4-substituted-2,2,6,6-tetramethyl-1-piperidinoxy preferably include 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinoxy, 4-methacryloyloxy-2,2,6,6-tetramethyl-1-piperidinoxy, 4-acetyloxy-2,2,6,6-tetramethyl-1-piperidnoxy and 4-acetylamino-2,2,6,6-tetramethyl-1-piperidinoxy, particularly preferably 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinoxy from the aspect of yield.
The base is free of any particular limitation as long as it does not interfere with the reaction, and is exemplified by sodium hydrogencarbonate, sodium carbonate, potassium hydrogencarbonate, potassium carbonate, lithium carbonate and the like, with preference given to sodium hydrogencarbonate and potassium hydrogencarbonate. The amount of the base to be used is generally 0.01 mol-2 mol, preferably 0.1 mol-0.9 mol, per 1 mol of compound [III].
Examples of the catalyst include phase transfer catalyst such as tetrabutylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium iodide, tetrabutylammonium sulfate, benzyltriethylammonium chloride, benzyltrimethylammonium chloride and the like, and metal halide catalyst such as potassium iodide, potassium bromide, sodium iodide, sodium bromide and the like, with preference given to tetrabutylammonium bromide, benzyltriethylammonium chloride, potassium iodide and potassium bromide. The amount of the catalyst to be used is generally 0.0001 mol-0.3 mol, preferably 0.01 mol-0.2 mol, per 1 mol of compound [III].
The organic solvent is not particularly limited and may be, for example, ethyl acetate, butyl acetate, acetone, ethyl methyl ketone, isobutyl methyl ketone, toluene, xylene, tert-butyl methyl ether and the like, with preference given to ethyl acetate, acetone, ethyl methyl ketone, isobutyl methyl ketone and toluene. The amount of the solvent to be used is generally 1 L-20 L, preferably 3 L-10 L, per 1 kg of compound [III].
The reaction temperature is generally from xe2x88x9230xc2x0 C. to 100xc2x0 C., preferably 0xc2x0 C.-50xc2x0 C., and the reaction time is generally 10 min-10 hr, preferably 10 min-2 hr.
The objective compound can be isolated by a conventional method such as extraction and crystallization.
The compound [VI] (5-phthalancarbonitrile compound) is an intermediate for the production of citalopram. It can be obtained by reacting a novel compound [IV] with hydroxylamine or a mineral acid salt thereof and via a novel compound [V] (compound [V] in the present invention includes both syn-compound and anti-compound), namely, through oximation (condensation) and dehydration reaction. It is preferable to (a) directly subject the compound [V] to dehydration reaction without isolation to make the manipulation simpler. For example, compound [IV] and hydroxylamine or a mineral acid salt thereof are added to an organic solvent and the mixture is heated as it is to give compound [VI].
For a higher purity of the compound [VI], (b) compound [V] is preferably isolated and then subjected to dehydration reaction. The compound [V] is obtained by reacting compound [IV] with hydroxylamine or a mineral acid salt thereof. By dehydrating compound [V], compound [VI] is obtained. To be specific, compound [IV] and hydroxylamine or a mineral acid salt thereof are added to an organic solvent, and the mixture is stirred to give compound [V]. The obtained compound [V] is isolated and heated to give compound [VI]. The compound [V] is isolated by a conventional method.
Examples of mineral acid salt of hydroxylamine include salts of hydroxylamine with hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid and the like, with preference given to hydroxylamine hydrochloride and hydroxylamine sulfate.
The amount of the hydroxylamine or a mineral acid salt thereof to be used is generally 0.8 equivalent-5 equivalents, preferably 0.9 equivalent-2 equivalents, per compound [IV]. The hydroxylamine and a mineral acid salt thereof are used as they are or preferably in a solution state (e.g., methanol, ethanol, isopropyl alcohol, water, etc.). Depending on the scale of the reaction, it is particularly preferably added dropwise as a solution of hydroxylamine or a mineral acid salt thereof in methanol at 20-50xc2x0 C.
Particularly when a hydroxylamine mineral acid salt is used, a suitable base is preferably added in an amount of 1 equivalent to 5 equivalents per hydroxylamine mineral acid salt. The base is free of any particular limitation as long as it exerts less influence on cyano, and examples thereof include organic base (e.g., triethylamine, tributylamine, dimethylaniline, pyridine, sodium methoxide, sodium ethoxide, potassium t-butoxide, sodium t-butoxide etc.), inorganic base (e.g., sodium carbonate, sodium hydrogencarbonate, sodium hydroxide, potassium carbonate, potassium hydrogencarbonate, potassium hydroxide etc.), with preference given to triethylamine. It is industrially preferable to add a base before the addition of a hydroxylamine mineral acid salt.
To carry out the dehydration reaction of compound [V] under mild conditions, a dehydrating agent may be further added. Examples of the dehydrating agent include acid anhydride (e.g., acetic anhydride, phthalic anhydride etc.), methanesulfonyl chloride, p-toluenesulfonyl chloride and the like, with preference given to the use of acetic anhydride from the aspects of the environment and yield. The amount of the dehydrating agent to be used is preferably 0.8 equivalent-5 equivalents, per hydroxylamine or a mineral acid salt thereof in the case of above (a), and 1 equivalent-10 equivalents, preferably 1 equivalent-5 equivalents, per compound [V] in the case of above (b). In the above (a), the dehydrating agent may be added simultaneously with hydroxylamine or a mineral acid salt thereof. However, the addition after the addition of hydroxylamine or a mineral acid salt thereof is preferable.
The organic solvent is free of any particular limitation as long as it does not interfere with the reaction, and examples thereof include methanol, ethanol, isopropyl alcohol, ethyl acetate, acetonitrile, toluene, xylene, chlorobenzene, 1,2-dichlorobenzene, N-methylpyrrolidone, nitroethane, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, dichloromethane, and mixed solvents of the above, with preference given to acetonitrile, toluene, xylene, N-methylpyrrolidone, nitroethane, ethyl acetate, a mixed solvent of ethyl acetate and methanol, a mixed solvent of ethyl acetate and ethanol, a mixed solvent of ethyl acetate and isopropyl alcohol, and a mixed solvent of toluene and methanol. The amount of the organic solvent to be used is generally 0.5 L-50 L, preferably 1 L-20 L, per 1 kg of compound [IV] in the case of above (a), and generally 0.5 L-50 L, preferably 1 L-20 L, per 1 kg of compound [IV] in the case of above (b).
The reaction temperature in the above (a) is generally 50xc2x0 C.-220xc2x0 C., preferably 80xc2x0 C.-150xc2x0 C., and the reaction time is generally 1 hr-20 hr, preferably 2 hr-8 hr.
In the above (b), oximation (condensation) is conducted generally at 20-120xc2x0 C., preferably 40-100xc2x0 C., generally for 10 min-4 hr, preferably 30 min-2 hr, and dehydration reaction is carried out generally at 60-160xc2x0 C., preferably 120-150xc2x0 C., more preferably 125-150xc2x0 C., generally for 30 min-8 hr, preferably 90 min-6 hr.
The objective compound is isolated by a conventional method such as extraction and crystallization after neutralization of the reaction mixture.
The starting compound [A] can be produced according to the method described in, for example, J. Phys. Org. Chem., 3(12), 789-98 (1990).
According to the method of the present invention, a 5-phthalancarbonitrile compound can be produced without using a reagent that imposes a great burden on the environment, such as heavy metal, metal cyanide and thionyl chloride. Moreover, the reaction proceeds efficiently throughout the entire steps.
The 5-phthalancarbonitrile compound can be converted to citalopram according to the method described in WO98/19511, thereby producing citalopram useful as an antidepressant.